Imaging apparatus

ABSTRACT

An imaging apparatus includes an image pickup device that includes a first pixel group configured to photoelectrically convert an object image formed by a luminous flux from an imaging optical system, and a second pixel group which includes a plurality of pixels configured to photoelectrically convert a split pair of the luminous flux from the imaging optical system and a detecting unit configured to implement a first detection control that changes an imaging state of the image pickup device while detecting a contrast of the object image based on an output of the second pixel group, and then a second detection control that changes the imaging state of the image pickup device while detecting the contrast of the object image based on an output of the first pixel group.

TECHNICAL FIELD

The present invention relates to an imaging apparatus, such as a digitalcamera and a video camera, and more particularly to an imaging apparatuswhich implements focus control by using an output from an image pickupdevice.

BACKGROUND ART

Japanese Patent Laid-Open No. (“JP”) 2000-156823 discloses an imagingapparatus configured to use an optical characteristic of a part ofpixels in an image pickup device in the imaging apparatus differentlyfrom other pixels and to implement focus detections based on an outputfrom the part of pixels.

The imaging apparatus disclosed in JP 2000-156823 arranges plural pairsof focus detection pixels in the part of the image pickup device. FIG. 6shows an illustrative pixel arrangement of an image pickup device thatarranges focus detection pixels in some part of rows in a pixel matrix.

In FIG. 6, R, G, and B are normal imaging pixels in which a red filter,a green filter, and a blue filter are respectively arranged. S1 and S2are first and second focus detection pixels which have different opticalcharacteristics from the imaging pixels.

FIG. 7 shows a structure of the first focus detection pixel S1. In FIG.7, a micro lens 501 is formed on the light incident side of the firstfocus detection pixel. 502 is a smoothing layer that has a flat surfaceconfigured to form the micro lens 501.

503 is a light shielding layer which includes a stop aperture part thatis decentered in one direction with respect to a center O of thephotoelectric conversion area 504 in the first focus detection pixel S1.

FIG. 8 shows a structure of the second focus detection pixel S2. In FIG.8, a micro lens 601 is formed on the light incident side of the secondfocus detection pixel. 602 is a smoothing layer that has a flat surfaceconfigured to form the micro lens 601.

603 is a light shielding layer which has a stop aperture part decenteredin an opposite direction from the light shielding layer 503 in the firstfocusing detection pixel S1 with respect to the center O of thephotoelectric conversion area 604 in the second focus detection pixelS2. In other words, the light shielding layers 503 and 603 in the firstand second focus detection pixels S1 and S2 include stop aperture partsthat are placed symmetrically with respect to the optical axis of eachmicro lens.

This structure provides an equivalent structure of symmetrical splittingof a pupil in the imaging optical system between the first focusdetection pixel S1 and the second focus detection pixel S2.

In FIG. 6, the rows which include the first focus detection pixels S1and those which include the second focus detection pixels S2 are setsuch that the two images can be closer to each other as the number ofpixels in the image pickup device increases. The rows including thefirst focus detection pixels S1 and those including the second focusdetection pixels S2 have the same outputs (or image signals) when theimaging optical system is in an in-focus state to the object.

On the other hand, when the imaging optical system is in an out-focusstate, a phase difference occurs between the image signals derived fromthe rows including the first focus detection pixels S1 and thoseincluding the second focus detection pixels S2. The phase-differencedirections are opposite between the front focus state and the back focusstate.

FIGS. 9A and 9B show relationships of focusing states and phasedifferences. In these figures, both focus detection pixels S1 and S2 aremoved closer to one another, and referred to as points A and B. Theimaging pixels are omitted.

A luminous flux from a specific spot on the object is split into aluminous flux Φ La that is incident upon a focus detection pixel A viathe split pupil corresponding to the focus detection pixel A and aluminous flux Φ Lb that is incident upon a focus detection pixel B viathe split pupil corresponding to the focus detection pixel B. These twoluminous fluxes are incident from the same point on the object, and canreach one point on the image pickup device via the same micro lens, asshown in FIG. 9A, when the imaging optical system is in the in-focusstate to the object. Accordingly, the image signals from the rowsincluding the first focus detection pixels A (S1) and those includingthe second focus detection pixels B (S2) correspond to one another.

However, in an out-focus state by a distance x shown in FIG. 9B,positions which the luminous fluxes Φ La and Φ Lb reach shift by anamount of change in the incident angles of Φ La and Φ Lb to the microlenses. Consequently, a phase difference occurs between the imagesignals from the rows including the first focus detection pixels A (S1)and those including the second focus detection pixels B (S2).

With the foregoing in mind, the imaging apparatus disclosed in JP2000-156823 implements focus control of a phase difference detectionmethod that utilizes the image pickup device.

JP 2001-305415 discloses an imaging apparatus that is suitable fordetections of a horizontal line and a vertical line of an object, andconfigured to implement both focus control of a phase differencedetection method that utilizes an output from the image pickup deviceand focus control of a contrast detection method.

However, the imaging apparatus disclosed in JP 2000-156823 has adifficulty in properly obtaining a phase difference or a defocus amountbecause two images formed on the first and the second focus detectionpixels are asymmetrical to one another as a defocus amount increases.

JP 2001-305415 discloses the imaging apparatus that applies a contrastdetection method to focus control when a defocus amount obtained by thephase difference method is less reliable, but this reference is silentabout proper use of the focus control of the contrast detection methodthat utilizes the focus detection pixels and the focus control of thecontrast detection method that utilizes pixels other than the focusdetection pixels.

DISCLOSURE OF INVENTION

The present invention provides an imaging apparatus that can implementboth focus control of a contrast detection method that utilizes a focusdetection pixel and focus control of a contrast detection method thatutilizes a pixel other than the focus detection pixel, in addition tofocus control of a phase difference detection method that utilizes afocus detection pixel.

An imaging apparatus according to one aspect of the present inventionincludes an image pickup device that includes a first pixel groupconfigured to photoelectrically convert an object image formed by aluminous flux from an imaging optical system, and a second pixel groupwhich includes a plurality of pixels configured to photoelectricallyconvert a split pair of the luminous flux from the imaging opticalsystem and a detecting unit configured to implement a first detectioncontrol that changes an imaging state of the image pickup device whiledetecting a contrast of the object image based on an output of thesecond pixel group, and then a second detection control that changes theimaging state of the image pickup device while detecting the contrast ofthe object image based on an output of the first pixel group.

A control method for an imaging apparatus according to another aspect ofthe present invention provides an image pickup device that includes afirst pixel group configured to photoelectrically convert an objectimage formed by a luminous flux from an imaging optical system, and asecond pixel group which includes a plurality of focus detection pixelsconfigured to photoelectrically convert a split one of the luminousfluxes from the imaging optical system. The control method includessteps of implementing a first focus control of a phase differencedetection method which utilizes an output of the second pixel group,implementing a second focus control of a contrast detection method whichutilizes an output of the first pixel group, implementing a third focuscontrol of a contrast detection method which utilizes an output of thesecond pixel group, and changing a focus control to be implemented amongthe first to third focus controls.

Other features and advantages of the present invention will be apparentfrom the following description given in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a configuration of a digital cameraaccording to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of an imaging pixel group anda focus detection pixel group according to the embodiment.

FIG. 3 is a flow chart of an operation of the camera according to theembodiment.

FIG. 4 is a diagram showing AF types of the camera according to theembodiment.

FIG. 5 is a flow chart of an operation of the AF types of the cameraaccording to the embodiment.

FIG. 6 is a diagram showing an arrangement of an imaging pixel group anda focus detection pixel group.

FIG. 7 is a diagram showing a structure of a first focus detectionpixel.

FIG. 8 is a diagram showing a structure of a second focus detectionpixel.

FIG. 9A is a schematic view of a phase difference in image signals inaccordance with an in-focus state.

FIG. 9B is a schematic view of a phase difference in image signals inaccordance with a (front) focus state.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the accompanying drawings, a description will be givenof an embodiment of the present invention.

FIG. 1 shows a configuration of a digital camera as an imaging apparatusaccording to one embodiment of the present invention.

A camera 100 includes an imaging optical system 101 which forms anobject image using a luminous flux from the object, a lens controller102 which controls a position of a focus lens (not shown) included inthe imaging optical system 101, a stop 103 which adjusts an incidentlight intensity from the imaging optical system 101, and an image pickupdevice 104 as a photoelectric conversion element that is comprised by aCMOS sensor having a light receiving surface on which the object imageis formed by a luminous flux from the imaging optical system 101.

The image pickup device 104 has any one of color filters R, G, and B,and an imaging pixel group (a first pixel group) 105 which has aplurality of imaging pixels for photoelectric conversions of the objectimage formed by the imaging optical system 101. The imaging pixel group105 outputs an imaging signal used to generate the object image. Theimage pickup device 104 has a focus detection pixel group (a secondpixel group) 106 which outputs a pair of image signals used to detect afocusing state (or for a focus detection) of the imaging optical system101.

The focus detection pixel group 106 includes a plurality of first andsecond focus detection pixels for photoelectric conversions of aluminous flux pupil-split by a pupil splitting optical system 107, whichwill be described later. The first phase difference sensor has aplurality of first focusing detection pixels, and the second phasedifference sensor has a plurality of second focus detection pixels. Thefirst phase difference sensor outputs one of the above pair of imagesignals whereas the second phase difference sensor outputs the other ofthe pair of image signals.

The image pickup device 104 includes a pupil splitting optical system107 configured to make a pupil-split luminous flux among the luminousfluxes from the imaging optical system 101 incident upon the first andsecond phase difference sensors.

FIG. 2 shows a pixel arrangement in the image pickup device 104 in thisembodiment. In FIG. 2, S1 is the first focus detection pixel, and S2 isthe second focus detection pixel in the focus detection group 106.

The first and second focus detection pixels S1 and S2 have similarstructures to those shown in FIGS. 7 and 8. In other words, the lightshielding layers in the first and the second focus detection pixels S1and S2 have stop aperture parts placed symmetrically to one another withrespect to the optical axis of the micro lens as a pupil splittingoptical system 107.

In FIG. 2, pixel rows into which the first focus detection pixels S1 arediscretely inserted form the first phase difference sensor. The pixelrows that are separated from the first phase difference sensor by apredetermined interval (or an interval of one pixel in FIG. 2) anddiscretely arrange the second focus detection pixels S2 form the secondphase difference sensor. One focus detection pixel group (second pixelgroup) including the first and second phase difference sensors form onefocus detection area. In FIG. 2, the first focus detection area and thesecond focus detection area are arranged on the top and the bottom ofthe image pickup device 104 respectively.

The camera 100 has a focus detector (or focus detecting unit) 108 whichcalculates a phase difference between a pair of image signals outputfrom the first and second phase difference sensors in each focusdetection area by applying a correlation operation.

The “pair of image signals output from the first and second phasedifference sensors (in other words, the focus detection pixel group106),” as used herein, means primarily a pair of image signals generatedexclusively from output signals of the focus detection pixels S1 and S2.A pair of image signals may also be generated from output signals of theentire focus detection pixel group.

The focus detector 108 further calculates, based on a phase difference,a defocus amount indicative of a focusing state of the imaging opticalsystem 101 to the object whose image is formed on the focus detectionarea.

In this embodiment, the focus detector 108 calculates a defocus amount,but the focus detector 108 may calculate a phase difference between theimage signals and the camera control part 117, which will be describedlater, may calculate a defocus amount based on the phase difference. Inaddition, this embodiment regards a focusing state as a defocus amount,but a phase difference may be regarded as a focusing state.

In this way, the focus detector 108 provides individual focus detectionsfor each focus detection area (or calculates a defocus amount).

As understood from FIGS. 7 and 8, the focus detection pixel group 106(including the first and second focus detection pixels S1 and S2) has alimited view by a light shielding layer provided to each pixel and hasno color filter. Accordingly, the level of the image signal from thefocus detection pixel group 106 is different from that of the imagesignal output from a plurality of pixels near the focus detection pixelgroup 106 (hereinafter referred as to an adjacent pixel group) in theimaging pixel group 105.

For this reason, the camera 100 has a gain controller 111 configured tocontrol a gain to the image signal from the focus detection pixel group106 in order to make the level of the image signal from the focusdetection pixel group 106 conform to that of the image signal from theadjacent pixel group.

The camera 100 further includes a spatial frequency detector (orfrequency component detector) 109 configured to detect the intensity ofa specific frequency component (or high frequency component) containedin the image signal from the adjacent pixel group (or imaging pixelgroup 105). The high frequency component represents a spatial frequencycomponent of an object image formed in the adjacent pixel group (or thefirst pixel group).

The camera 100 further includes a determination switch 110. Thedetermination switch 110 switches a determination criterion of aninterpolation performed at a pixel interpolator 112, which will bedescribed later, between the focusing state detected by the focusdetection pixel group 106 and the intensity of the high frequencycomponent detected by the spatial frequency detector 109.

The pixel interpolator (or image generator) 112 interpolates andgenerates image data corresponding to the focus detection pixel group106 based on an output of the adjacent pixel group. In other words,based on the output of the imaging pixel group 105 (the adjacent pixelgroup), the pixel interpolator 112 generates a partial imagecorresponding to the focus detection pixel group 106 among the entireimage obtained from an output from the image pickup device 104.

The “image data corresponding to the focus detection pixel group 106 (orthe partial image)” may be image data to an area which entirely coversthe focus detection pixel group 106 or image data for each of the focusdetection pixels S1 or S2.

The camera 100 further includes an image processor 113 configured toprovide image processes, such as a gamma correction, a white balanceadjustment, resampling for display, and an image compression andencoding to an image signal output from the imaging pixel group 105.

The camera 100 further includes a display 114 configured to display(still) image data output from the image processor 113, a recorder 115configured to record image data in a recording medium, such as asemiconductor memory or an optical disc, an operating part 116 whichaccepts a user's inputs, and a camera controller 117 as a controllerconfigured to control the entire camera 100.

The camera controller 117 calculates a driving amount of the focus lensso as to obtain in-focus based on a defocus amount obtained from thefocus detector 108. The calculated driving amount is output to the lenscontroller 102, which, in turn, moves the focus lens based on thedriving amount.

In this way, as shown in a circle “1” in FIG. 4, the camera controller117 applies AF of a phase difference detection method (which is firstfocus control simply referred to as a “phase difference AF” hereinafter)which utilizes an output (or image signal) from the focus detectionpixels 106 so as to obtain an in-focus state. However, this phasedifference AF has a wider in-focus range than AF of a contrast detectionmethod, which will be described later.

The camera 100 further includes a sharpness detector 118. The sharpnessdetector 118 detects (or extracts) a high frequency component containedin an image signal from the imaging pixel group 105 or the focusdetection pixel group 106. Then, the sharpness detector 118 generatesfocus assessment information (or an AF assessment value signal) based onthe high frequency component, and outputs it to the camera controller117. The focus assessment information represents a contrast state of anobject image, in other words, sharpness.

The camera controller 117 obtains the in-focus state by moving the focuslens to a position that provides the largest value of the focusassessment information. This is the contrast detection method AF, andthe in-focus state can be obtained more precisely and rapidly whencombined with the phase difference AF.

For example, the camera controller 117 initially performs the phasedifference AF, and moves the focus lens to the vicinity of an in-focusposition. Next, the camera controller 117 performs AF of a contrastdetection method, and moves the focus lens to a more precise in-focusposition. The AF of the contrast detection method is also effective inmaintaining the in-focus state when the camera 100 takes motionpictures.

This embodiment may provide, as shown in a circle “2” in FIG. 4, AF of acontrast detection method (which is second focus control simply referredto as an “imaging pixel contrast AF” hereinafter) that utilizes anoutput (or imaging signal) from the imaging pixel group 105. Analternative embodiment may provide, as shown in a circle “3” in FIG. 4,AF of a contrast detection method (which is third focus control simplyreferred to as a “focus detection pixel contrast AF” hereinafter) whichutilizes an output (or image signal) from the focus detection pixelgroup 106.

In the focus detection pixel contrast AF, any one of the outputs fromthe first and second focus detection pixels S1 and S2 may be used, orthese outputs may be alternately used.

FIG. 3 shows an operation of the camera 100 (mainly the cameracontroller 117) according to this embodiment. The operation isimplemented in accordance with a computer program which is stored in amemory (not shown) in the camera controller 117.

The camera controller 117 starts an operation from the step S301 inresponse to an AF command signal (e.g., a signal output by pressing arelease button halfway) input by the operating part 116. Although notspecifically described, an imaging preparation, such as an exposurecalculation, is operated parallel to the AF operation.

In the step S301, the camera controller 117 implements an AF operation.When a defocus amount before the AF operation is implemented is small,the in-focus state is available by the phase difference AF whichutilizes an output from the focus detection pixel group 106 describedabove. However, if a defocus amount before the AF operation isimplemented is large, two images formed on the first and second focusdetection pixels (or phase difference sensors) are asymmetrical to oneanother, and it will be difficult to accurately obtain a phasedifference or a defocus amount.

For this reason, in the step S301, this embodiment performs the AFoperation shown in FIG. 5.

In the step S401 shown in FIG. 5, the camera controller 117 instructsthe focus detection pixel group 106 in the image pickup device 104 toinitiate charge accumulations. After the charge accumulations arecompleted, the camera controller 117 outputs an image signal from thefocus detection pixel group 106 to the focus detector 108. As describedabove, the focus detector 108 calculates a defocus amount, and outputsit to the camera controller 117. The camera controller 117 obtains thedefocus amount from the focus detector 108.

Next, in the step S402, the camera controller 117 determines whether ornot the obtained defocus amount is larger than a predetermined amount.If the defocus amount is smaller than the predetermined amount, the flowproceeds to the step S405 which implements the phase difference AF “1.”

If the defocus amount is larger than the predetermined amount, the flowproceeds to the step S403 in which the camera controller 117 implementsthe focus detection pixel contrast AF “3.” Then, the flow proceeds tothe step S404.

In the step S404, the camera 117 implements the imaging pixel contrastAF “2.” In this way, the flow proceeds to the step S302 when the defocusamount precisely reduces to the level of the in-focus state.

When the in-focus state is precisely obtained by the focus detectionpixel contrast AF “3,” the imaging pixel contrast AF “2” may be omitted.In other words, the imaging pixel contrast AF “2” may follow when thefocus detection contrast AF “3” cannot provide the sufficiently precisein-focus state.

Thus, this embodiment can provide the in-focus state by the contrast AFwhich effectively utilizes the focus detection pixel group 106 byimplementing the focus detection pixel contrast AF “3” and the imagingpixel contrast AF “2” even if the defocus amount is large. In otherwords, a proper in-focus state regardless of the level of the defocusamount is available through switching of the phase difference AF whichutilizes the output from the focus detection pixel group 106, the focusdetection pixel contrast AF “3,” and the imaging pixel contrast AF “2.”

Although this embodiment discusses switching of AF to be implementedamong the AFs “1” to “3” according to the defocus amount, the AF to beimplemented may be switched according to the object. For example, aswill be described later, since the phase difference AF is less viablewhen the object has a repetitive pattern, the contrast AFs “2” and “3”may be implemented.

Since it is conceivable that an exposure condition may change due to achange in an object image after the AF operation moves the focus lens,the exposure calculation is repeated at a new focus-lens position, andthe flow proceeds to the step S302.

In the step S302, the camera controller 117 determines whether or not animaging command signal (e.g., a signal output by completely pressing arelease button) is input from the operating part 116. If the imagingcommand signal has not yet been input, the determination of this step isrepeated. When the imaging command signal is input, the flow proceeds tothe step S303.

In the step s303, the camera controller 117 instructs the imaging pixelgroup 105 and the focus detection pixel group 106 in the image pickupdevice 104 to initiate charge accumulations. After the chargeaccumulations are completed, the camera controller 117 outputs an imagesignal of the image pickup device 105 to the spatial frequency detector109 and the pixel interpolator 112, and outputs an image signal of thefocus detection pixel group 106 to the focus detector 108 and the gaincontroller 111. After these outputs are made, the flow proceeds to thestep S304.

In the step S304, the camera controller 117 initializes a counter (n=1).A numerical value of the counter, “n” corresponds to “n” focus detectionareas in the image pickup device 104.

In the step S305, the camera controller 117 and the determination switch110 determine whether or not the focus detection can be made in then^(th) focus detection area. If a defocus amount is obtained based on aphase difference between the image signals obtained from the focusdetection pixels 106, the focus detection may not be properlyimplemented for an object having a repetitive pattern. Whether the imagedata interpolation is available according to the defocus amount cannotbe determined based on the improper focus detection. Therefore, in sucha case, this embodiment determines the availability of the image datainterpolation based on a detection result of a high frequency componentdetected by the spatial frequency detector 109. This is because a highintensity of the high frequency component can be regarded as a smalldefocus amount in the imaging optical system 101.

The flow proceeds to the step S306 when the focus detection is availablein the n^(th) focus detection area, but proceeds to the step S311 whenthe focus detection is unavailable.

In the step S306, the camera controller 117 obtains a defocus amount inthe n^(th) focus detection area from the focus detector 108, anddetermines whether or not the defocus amount is smaller than apredetermined threshold (or first predetermined value). Thisdetermination also determines whether a spatial frequency of the objectimage formed on the n^(th) focus detection area has a value enough for agood entire image through the image data interpolation by the pixelinterpolator 112 configured to generate the image data which correspondsto the focus detection area (or focus detection pixel group 106).

Usually, an image signal (or object image) having a large defocus amounthas a small amount of high frequency component (low contrast). On theother hand, an image signal (or object image) having a small defocusamount (near the in-focus state) has a large amount of high frequencycomponent (high contrast). As described above, a drop of the sharpnessof the image is not so conspicuous when the pixel interpolator 112interpolates image data with a low spatial frequency of the objectimage, but that is conspicuous when the pixel interpolator 112interpolates the image data with a high spatial frequency of the objectimage.

Accordingly, this embodiment controls the image data interpolation bythe pixel interpolator 112 according to a level of a defocus amount whenthe focus detection has been successful: The flow proceeds to the stepS307 without the image data interpolation for a defocus amount smallerthan the threshold, and proceeds to the step S309 with the image datainterpolation for a defocus amount equal to or larger than thethreshold.

In the step S307, the camera controller 117 compares an average imagesignal in the n^(th) focus detection area (referred to as an “n^(th)focus detection pixel group 106” hereinafter) with an average imagesignal in the adjacent pixel group. Then, the gain controller 111controls a gain applied to the image of the n^(th) focus detection pixelgroup 106 such that these signal levels are identical or deemed to beidentical. Alternatively, peak values of the image signals may becompared rather than comparing the average image signals of the pixelgroup with each other. The flow proceeds to the step S308 after the gainis thus controlled.

In the step S308, the camera controller 117 inserts an image signal ofthe n^(th) focus detection pixel group 106 in which the gain iscontrolled in the step S307, into an area (or position) whichcorresponds to the n^(th) focus detection pixel group 106 in the imagesignal of the imaging pixel group 105. This step can generate syntheticimage data that synthesizes an image based on an image signal from theimaging pixel group 105 with a partial image based on the(gain-controlled) image signal from the n^(th) focus detection pixelgroup 106. The camera controller 117 outputs the synthesized image datato the image processor 113. Then, the flow proceeds to the step S313.

In the step S309, the camera controller 117 directs the pixelinterpolator 112 to generate the partial image data for theinterpolation corresponding to the n^(th) focus detection pixel group106 through an interpolation calculation using the image signal of theadjacent pixel group of the n^(th) focus detection pixel group 106. Inother words, the image interpolator 112 generates the partial imagecorresponding to the n^(th) focus detection pixel group 106, among theentire image obtained by the output from the image pickup device 104,based on the output of the imaging pixel group 105 (the adjacent pixelgroup).

This embodiment needs to interpolate a pixel signal of a green componentparticularly for the focus detection pixels S1 and S2 due to theperiodic color-filter arrangement of the imaging pixel group 105.Accordingly, pixel signals corresponding to the positions of the focusdetection pixels S1 and S2 are generated based on signals having greencomponents which are adjacent in oblique directions to the focusdetection pixels S1 and S2 of the adjacent pixel group in FIG. 2. Thesurrounding pixels used for the interpolation are not limited to thosehaving green components, which are adjacent in oblique directions to thefocus detection pixels S1 and S2 described above. In other words, anedge may be detected from a positional change of a signal level and theinterpolation calculation that takes the edge position of the objectimage into account may be made by using distant pixels having greencomponents.

The flow proceeds to the step S310 after the partial image data for theinterpolation is generated.

In the step S310, the camera controller 117 inserts an image signal onthe partial image data for the interpolation for the n^(th) focusdetection pixel group 106 generated in the step S309, into an area (orposition) which corresponds to the n^(th) focus detection pixel group106 in the image signal of the imaging pixel group 105, thereby creatingsynthesized image data between the image based on the image signal fromthe imaging pixel group 105 and the partial image for the interpolationfor the n^(th) focus detection pixel group 106. The camera controller117 outputs the synthesized data to the image processor 113. Then, theflow proceeds to the step S313.

In the step S311, the camera controller 117 directs the spatialfrequency detector 109 to detect a high frequency component from theimage signal of the adjacent pixel group for the n^(th) focus detectiongroup 106.

In the step S312, the camera controller 117 determines whether or notthe intensity of the high frequency component detected in the step S311is higher than a predetermined threshold (or a second predeterminedvalue).

If the intensity of the high frequency component is higher than thethreshold as described above (or when the contrast is high), the defocusamount of the imaging optical system 101 is considered small. Then, thestep S305 can provide focus detection, and the step S306 operates as ifthe defocus amount is smaller than the threshold. On the other hand, ifthe intensity of the high frequency component is lower than thethreshold (or when the contrast is low), the defocus amount of theimaging optical system 101 is considered large. Then, the step 305 canprovide focus detection, and the step S306 operates as if the defocusamount is greater than the threshold.

In other words, the flow proceeds to the step S307 without the imagedata interpolation when the detected intensity is higher than thethreshold, and proceeds to the step S309 for the image datainterpolation if the detection intensity is lower than the threshold.

In the step S313, the camera controller 117 determines whether or notthe processes in the steps S305 to S312 are completed to all or “n”focus detection areas. The flow proceeds to the step S314, and returnsto the step S305, after incrementing a counter value by one when theprocesses are not completed to all of the focus detection areas.Thereby, the above processes are performed for the next focus detectionarea. On the other hand, the flow proceeds to the step S315 if theprocesses are completed to all of the focus detection areas.

In the step S315, the camera controller 117 directs the image processor113 to implement a gamma correction, a white balance adjustment,resampling for display, and an image compression and encoding to thesynthesized image data. The image processor 113 outputs the image datain which the above processes are implemented, to the display 114. Thedisplay 114 displays the image data in order to make a user check thetaken image.

The image processor 113 further outputs the image data in which theabove processes are implemented to the recorder 115. The recorder 115records the image data in the recording medium.

The above operation can provide a good image having a high degree ofsharpness even if the image pickup device 104 has many focus detectionpixels.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims a foreign priority benefit based on JapanesePatent Application 2007-238948, filed on Sep. 14, 2007, which is herebyincorporated by reference herein in its entirety as if fully set forthherein.

FIELD OF INDUSTRIAL APPLICATION

The present invention provides an imaging apparatus that can implementboth focus control of a contrast detection method that utilizes a focusdetection pixel and focus control of a contrast detection method thatutilizes a pixel other than the focus detection pixel, in addition tofocus control of a phase difference detection method that utilizes afocus detection pixel.

1. An imaging apparatus comprising: an image pickup device that includesa first pixel group configured to photoelectrically convert an objectimage formed by a luminous flux from an imaging optical system, and asecond pixel group which includes a plurality of pixels configured tophotoelectrically convert a split pair of the luminous flux from theimaging optical system; and a detecting unit configured to implement afirst detection control that changes an imaging state of the imagepickup device while detecting a contrast of the object image based on anoutput of the second pixel group, and then a second detection controlthat changes the imaging state of the image pickup device whiledetecting the contrast of the object image based on an output of thefirst pixel group.
 2. An imaging apparatus comprising: an image pickupdevice that includes a first pixel group configured to photoelectricallyconvert an object image formed by a luminous flux from an imagingoptical system, and a second pixel group which includes a plurality ofpixels configured to photoelectrically convert a split pair of theluminous flux from the imaging optical system; and a controllerconfigured to selectively implement one of a first focus control of aphase difference detection method that utilizes an output of the secondpixel group, a second focus control of a contrast detection method thatutilizes an output of the first pixel group, and a third focus controlof a contrast detection method that utilizes an output of the secondpixel group.
 3. An imaging apparatus according to claim 2, wherein thecontroller selects the first focus control or a combination of thesecond and third focus controls based on a defocus amount of the imagingoptical system.
 4. An imaging apparatus according to claim 3, whereinthe controller implements the first focus control when the defocusamount is smaller than a threshold, and implements the second and thirdfocus controls when the defocus amount is larger than the threshold. 5.An imaging apparatus according to claim 2, wherein the controllerimplements the third focus control prior to the second focus control inimplementing the second and third focus controls.
 6. A control methodfor an imaging apparatus which provides an image pickup device thatincludes a first pixel group configured to photoelectrically convert anobject image formed by a luminous flux from an imaging optical system,and a second pixel group which includes a plurality of focus detectionpixels configured to photoelectrically convert a split one of theluminous fluxes from the imaging optical system, the control methodcomprising steps of: implementing a first focus control of a phasedifference detection method which utilizes an output of the second pixelgroup; implementing a second focus control of a contrast detectionmethod which utilizes an output of the first pixel group; implementing athird focus control of a contrast detection method which utilizes anoutput of the second pixel group; and changing a focus control to beimplemented among the first to third focus controls.